Fiber optic circuit and module with switch

ABSTRACT

A fiber optic circuit provides signal access and monitoring. A module housing the circuit and the module is mountable to a chassis. The module housing includes mounting flanges for mounting the module to the chassis; and a plurality of exposed adapters along at least one of the front and rear faces. Each of the plurality of adapters is connectable to a fiber optic connector external to the module. The plurality of adapters define first and second transmit signal ports and first and second receive signal ports. A transmit signal pathway is between the first and second transmit signal port. A receive signal pathway is between the first and second receive signal ports. A first switch, such as a 2×2 switch, is between the transmit and receive signal pathways wherein the switch has first and second states, the first state being a normal through state wherein the first and second transmit signal ports are in communication along the transmit signal pathway, and wherein the first and second receive signal ports are in communications along the receive signal pathway, and a loopback state wherein the first transmit signal and the receive signal port are in communication along a first loopback path along a portion of the transmit and receive signal pathways, and wherein the second transmit and receive signal ports are in communication along a loopback path along other portions of the transmit and receive signal pathways. A second 2×2 switch or a 1×2 switch allows access for testing with test equipment and a 1×N optical switch. The various switches can be remotely controlled.

FIELD OF THE INVENTION

[0001] The present invention relates to fiber optic circuits and modulesfor fiber optic equipment.

BACKGROUND OF THE INVENTION

[0002] The telecommunications and data transmission industries arerapidly expanding their development of fiber optic transmission systems.Historically, telecommunications signals and data have been transmittedover wire lines such as twisted pair or coaxial cables. In order toaccommodate higher signal rate speeds, the industry is turning toincreased use of fiber optic cables as the transmission medium.

[0003] As the use of fiber optic cables increases, the need forperipheral equipment has increased. For example, it is desirable to haveaccess to a fiber optic line for the purpose of either re-routing theline in the event of damage to the line or to have access to the linefor the purposes of monitoring or testing the line.

[0004] Fiber optic peripheral equipment for cable management, cablestorage, and connection capabilities are well known. The use of modularfiber optic connector modules is known for performing so-calledcross-connect applications. U.S. Pat. Nos. 5,432,875 and 5,363,465 toADC Telecommunications, Inc. concern fiber optic connector modules andchassis designs for receiving the modules in cross-connect applications.

[0005] There is a continuing need for fiber optic circuits and systemswhich provide optical signal routing, monitoring, and accesscapabilities.

SUMMARY OF THE INVENTION

[0006] The present invention includes an optical circuit for connectingfiber optic cables and/or equipment, including one or more switches inthe optical circuit for changing the optical signal paths of thecircuit. The switch or switches can be used to selectively link theoptical signal paths to access terminals, such as for signal testing,monitoring or re-routing. The optical circuit may allow for one or moreof the following functions for signals passing through the circuit:passing through of the signals, non-intrusive monitoring of the signals,looping back of the signals between the transmit and receive terminals,and splitting of the signals, such as in combination with testequipment.

[0007] One circuit of the present invention includes two optical signalpathways and a switch between the two signal pathways allowing normalpass through of the signals along each signal pathway in one state, andlooping back of the signals in a second state. Access to one or both ofthe signal pathways can be provided to the circuit by non-intrusivemonitors, or switches, such as 1×2 switches or 2×2 switches.

[0008] Remote control of the one or more switches in the opticalcircuits of the present invention allows for remote test access, in onepreferred system.

[0009] The optical circuits of the present invention can be housed inone or more housings, as desired. Modular housings allow for convenientassembly, use and maintenance of the system.

[0010] In accordance with the invention, one preferred embodimentincludes one or more fiber optic modules which are mountable to achassis for holding one or more modules. Each module may have aplurality of connection locations for coupling to fiber opticconnectors. The connection locations are linked together by opticalcouplers within the module. Telecommunications cables and equipment areconnected to first sets of the connection locations of the modules. Themodules may be used to cross-connect fiber optic equipment via patchcords between second sets of the connection locations, or the secondsets of the connection locations may be connected together within asingle module.

[0011] One preferred embodiment of the fiber optic module of the presentinvention includes a first pair of adapters for connection to fiberoptic connectors and a second pair of adapters for connection to furtherfiber optic connectors. The first and second pairs of adapters areconnected by fiber optic signal pathways through the module. One adapterof each pair may define a transmit signal port, and the other adapter ofeach pair may define a receive signal port. The first pair of adaptersmay be connected to a cable entering a customer's facility. The secondpair of adapters may be cross-connected to another module at thecustomer's facility, or the adapters may be connected to other fiberoptic equipment.

[0012] One preferred embodiment of the fiber optic module includes afirst switch between the first and second signal pathways wherein bothpathways are in a straight pass through configuration when the switch isin a first state, and wherein both pathways are linked to form two loopback pathways through the module when the switch is in a second state.One preferred embodiment includes a 2×2 optical switch.

[0013] One further preferred embodiment of a fiber optic module includesa third pair of adapters, such as for use in connecting to test oraccess equipment. A second switch links the third pair of adapters toeither the transmit signal pathway or the receive signal pathway. Thesecond switch has at least two states, wherein a first state of thesecond switch optically links one adapter of the third pair to the otheradapter of the third pair in a loop back configuration. A second stateof the second switch optically links one adapter of the third pair ofadapters to one of the adapters of the first pair, and the other adapterof the third pair is optically linked to the first switch. Splitters andmonitor ports may be linked to the transmit and receive signal pathwaysin preferred embodiments.

[0014] In an alternative preferred embodiment, a single additionaladapter may be provided, instead of the third pair of adapters, and asingle 1×2 optical switch provided in either the transmit or receivesignal pathways. The 1×2 switch optically isolates the third adapter inone state, and optically links the additional adapter to the firstswitch when the 1×2 switch is in a second state. Splitters and monitorports may be linked to the transmit and receive signal pathways inpreferred embodiments.

[0015] Further embodiments of the invention include an optical circuitincluding first and second pairs of connection locations, each pairdefining a transmit signal connection location and a receive signalconnection location. The transmit signal connection location of eachpair is optically linkable through a signal path to the receive signalconnection location of the other pair. One or more access connectionlocations are provided which are linkable to one of the signal pathsthrough the circuit. One or more switches may be provided to selectivelylink the access connection location(s) to one of the signal paths. Afirst switch, such as a 2×2 switch, between the signal paths, and asecond switch, such as a 1×2 or a 2×2 switch between one of the signalpaths and the access connection location(s) are provided. The first andsecond pairs of connection locations defining the transmit and receivesignal connection locations may be part of a single module or housingconstruction in a frame, rack or chassis, or they may be part ofseparate modules or housing constructions cross-connected togetherthrough optical signal pathways, such as patch cords or other opticallinks.

[0016] The circuits of the present invention may be used in a variety ofapplications, such as for looping back of signals, or for splittingsignals in combination with test equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In the drawings, wherein like reference letters and numeralsindicate corresponding elements throughout the several views:

[0018]FIG. 1A is a schematic diagram of an optical circuit in accordancewith the invention;

[0019]FIG. 1 is a schematic diagram of a first embodiment of a fiberoptic access module in accordance with the present invention;

[0020]FIG. 2 is a schematic representation of various features which maybe provided with various fiber optic access modules in accordance withthe present invention;

[0021]FIG. 3 is a schematic representation of two fiber optic accessmodules cross-connected together, and showing various features which maybe provided with the various fiber optic modules of the presentinvention;

[0022]FIG. 4 is a schematic diagram of a control system for remotelycontrolling the optical switches in the fiber optic access modules;

[0023]FIG. 5 is a perspective view of a chassis showing two fiber opticaccess modules mounted thereto;

[0024]FIG. 6 is a rear perspective view of the chassis and modules shownin FIG. 5;

[0025]FIG. 7 is a front view of the single circuit fiber optic accessmodule;

[0026]FIG. 8 is a front perspective view of the module of FIG. 7;

[0027]FIG. 9 is a rear perspective view of the module of FIG. 7;

[0028]FIG. 10 shows two alternative fiber optic access modulescross-connected together, and connected to fiber optic test equipment;

[0029]FIG. 11 shows the two modules of FIG. 10 in a transparent ornormal mode;

[0030]FIG. 12 shows the two modules of FIG. 10 in a loopback mode withrespect to the fiber optic terminals;

[0031]FIG. 13 shows the two modules of FIG. 10 in a loopback mode withrespect to the test equipment;

[0032]FIG. 14 shows the first module of FIG. 10 in a split loopback modewith respect to the test equipment;

[0033]FIG. 15 shows the second module of FIG. 10 in a split loopbackmode with respect to the test equipment;

[0034]FIG. 16 shows both modules of FIG. 10 in the split loopback mode,as shown in FIG. 14 and 15;

[0035]FIG. 17 shows the first module of FIG. 10 in a split mode wherethe transmit signal of the second module is received by the testequipment connected to the first module;

[0036]FIG. 18 shows the second module of FIG. 10 in a split mode wherethe transmit signal of the first module is received by the testequipment connected to the second module;

[0037]FIG. 19 shows both modules of FIG. 10 in the split mode, as shownin FIGS. 17 and 18;

[0038]FIG. 20 shows both modules of FIG. 10 in a monitor mode withrespect to the test equipment;

[0039]FIG. 21 is a schematic diagram of a second embodiment of a fiberoptic access module including a 2×2 loopback switch, and a 1×2 splitswitch positioned in the transmit signal pathway;

[0040]FIG. 22 is a schematic representation of various options for themodule of FIG. 21;

[0041]FIG. 23 is a schematic representation showing various options fortwo modules of the type shown in FIG. 22 cross-connected together;

[0042]FIG. 24 shows two fiber optic access modules cross-connectedtogether of the type shown in FIG. 21, and also shown connected to fiberoptic test equipment;

[0043]FIG. 25 shows a modification to one of the modules of FIG. 24,where a 2×2 switch has been eliminated;

[0044]FIG. 26 shows the two modules of FIG. 25 showing the loopbackpathways for the primary signals;

[0045]FIG. 27 shows the two modules of FIG. 24 showing the split andloopback pathway for the module lacking the 2×2 switch;

[0046]FIG. 28 is a schematic diagram of a third embodiment of a fiberoptic access module including a 2×2 loopback switch, and two 1×2 splitswitches, one positioned in each primary signal pathway;

[0047]FIG. 29 shows the module of FIG. 28 connected to fiber optic testequipment;

[0048] FIGS. 30-39 show various applications of the module of FIG. 29.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] Referring now to FIG. 1A, a schematic representation of anoptical circuit 1 in accordance with the present invention is shownincluding two optical signal pathways 2, 3 linking connection locations4 a and 4 c, and 4 b and 4 d, respectively. Connection locations 4 a-dmay be any type of fiber optic connection system including fiber opticconnectors/adapters, fiber optic splices, or other fiber opticconnection system for transmitting fiber optic signals. A switch 5between the two signal pathways 2, 3 allows normal passing through ofthe signals along each signal pathway in one state, and looping back ofthe signals in a second state. In the looping back state, connectionlocation 4 a can communicate with connection location 4 b, andconnection location 4 c can communicate with connection location 4 d.One example switch 5 is a 2×2 optical switch. Access to one or both ofthe signal pathways 2, 3 can be provided to the circuit by accessarrangement 6, shown in the example as providing access to signalpathway 3. Preferably, access arrangement 6 provides an optical linkbetween signal pathway 3 and connection locations 4 e and 4 f. Access tosignal pathway 3 can be provided by a variety of devices includingnon-intrusive monitors and/or switches, such as 1×2 switches or 2×2switches. Access to other portions of signal pathway 3, such as betweenswitch 5 and connection location 4 d can also be provided instead of orin addition to access arrangement 6. Similarly, access arrangements canbe provided in signal pathway 2, in a similar manner. Circuit 1 has avariety of applications in fiber optic systems where access to one ormore of the fiber optic pathways is desired.

[0050] Referring now to FIG. 1, a first preferred embodiment of a fiberoptic module 10 using the circuit features of FIG. 1A is shown forcross-connecting fiber optic cables, and for providing test and accesslocations. Module 10 includes an optical circuit 11 including a transmitsignal pathway 12 and a receive signal pathway 14 extending betweenfiber optic terminals or ports 16 and cross-connect terminals or ports18. Specifically, fiber optic terminals (FOT) 16 include a transmitterminal T1 and a receive terminal R1. Cross-connect terminals 18include transmit terminal T2 and receive terminal R2. Preferably, module10 includes access terminals or ports for allowing access to signalspassing through module 10. For example, test equipment and/or monitorscan be optically linked to one of the transmit or receive signalpathways 12, 14. In the embodiment of FIG. 1, test equipment 20, andmonitor 22 is linked to transmit signal pathway 12.

[0051] While use of two modules cross-connected together is shown inFIGS. 1-27, it is to be appreciated that circuit 11 can be mounted inother module housings, racks or frames, and circuit 11 can be part of alarger circuit within the same module housing, rack or frame as desired.

[0052] One or more switches are provided to selectively connect anddisconnect the various signal pathways within module 10. For example, afirst switch 24 is positioned to selectively connect and disconnecttransmit signal pathway 12 with receive signal pathway 14. Further,switch 24 disconnects the connection between terminals T1 and T2, andterminals R1 and R2, when transmit signal pathway 12 is linked toreceive signal pathway 14. A 2×2 optical switch is one preferredstructure for switch 24.

[0053] As shown in FIG. 1, a second 2×2 optical switch is providedbetween terminal T1 and first switch 24. Second switch 30 allows anormal through path along transmit signal pathway 12 between terminalsT1 and T2. Switch 30 further provides a loopback pathway betweenpathways 26 and 28 so as to optically link receive terminal R3 withtransmit terminal T3 of test equipment 20. When second switch 30 isplaced in a second state, transmit signal pathway 12 is interrupted andterminal T1 becomes optically linked with terminal R3, and terminal T3becomes optically linked with terminal T2.

[0054] In module 10 of FIG. 1, a splitter 32 splits a portion of thesignal from transmit signal pathway 12 and diverts it to a monitorpathway 34 optically linked to monitor terminal T1. Access to monitorpathway is by monitor terminal R4. One preferred splitter is a 90%-10%type splitter, although any percentage splitter is useable.

[0055] Module 10 can be utilized in five modes of operation if desired:normal, loopback, split/loopback, split, and monitor. In the normal modeof operation, first and second switches 24, 30 will be positioned sothat the signals flow from terminals T1 to T2, and from terminals R2 toR1. The normal mode of operation also provides a loopback of the testequipment through second switch 30. Monitor mode is present at all timesto monitor the signal in transmit signal pathway 12.

[0056] When the first switch 24 is in the loopback position, and thesecond switch 30 is in the normal position, module 10 is in the loopbackmode. The signals flow from terminals T1 to R1, from terminals T2 to R2,and from terminals T3 to R3.

[0057] When the first switch 24 is in the loopback position and thesecond switch 30 is in the split position, module 10 is in thesplit/loopback mode. The signals flow from terminals T1 to R3, fromterminals T2 to R2 and from terminals T3 to R1.

[0058] When the second switch 30 is in the split position and the firstswitch 24 is in the normal position, module 10 is in the split mode. Thesignals flow from terminals T1 to R3, from terminals T3 to T2, and fromterminals R2 to R1.

[0059]FIG. 2 illustrates schematically various features for module 10′.Module 10 of FIG. 1 is one embodiment of module 10′. Module 10′ includesa 2×2 switch 32 in receive signal pathway 14. Typically, although notrequired, such a switch would be provided instead of second switch 30.Also, other monitors 22 a, 22 b, 22 c may be provided at various pointsin the transmit and receive signal pathways 12, 14, if desired.Generally, module 10′ would not likely exist with all of the featuresshown. FIG. 2 is provided to illustrate the wide variety of functionsthat could be provided as desired to access and monitor the varioussignal pathways at various points in the module. FIG. 3 showsschematically the module 10′ representation of FIG. 2 cross-connected atcross-connection location 40 to a second module 10″.

[0060] Referring now to FIG. 4, the optical switches 24, 30 of module 10can be operated remotely, if desired. Remote control is useful forremote accessing with test equipment. Alternatively, switches could beoperated manually. In the case of remote control, control logic 50 isprovided for each module 10 ₁, 10 ₂. . . 10 _(n). Links 52, 54 betweencontrol logic 50 operate each switch 24, 30. A network control/database60 controls each control logic 50 ₁, 50 ₂. . . 50 _(n) by a link 58.Link 58 can be by ethernet, RS232, RS485, or other links. FIG. 4 alsoillustrates distributed control by controller 62 which may providecentral local control of control logic 50 of each module 10 throughlinks 63.

[0061] Referring now to FIGS. 5-9, a fiber optic chassis 70 is shown forholding a plurality of the fiber optic modules 10. Chassis 70 ismountable to a rack (not shown) for holding chassis 70. Chassis 70includes an outer housing 72 and a pivotally mounted front door (notshown) hinged at hinge 74. Front door allows access to an interior ofchassis 70, so as to access individual modules 10 such as for repair orreplacement of modules 10 or to connect or disconnect the modules withother modules or fiber optic equipment. Chassis 70 includes a pluralityof guides 76 for holding the individual modules 10 in a horizontalmanner. Side opening 78 and cable clips 79 allows for cable pathwaysinto and out of chassis 70.

[0062] Modules 10 have connection locations, terminals or ports 80 alongthe front and the rear. The modules 10 may be used for interconnectingthe fiber optic equipment as desired, instead of through a traditionalcross-connect connection.

[0063] Module 10 has a module housing 90 including a front face 92 andan opposite facing rear face 94. The front and rear faces 92, 94 eachdefine connection locations 80 for connecting module 10 to fiber opticcables. In the embodiment shown, the front connection locations 80 areangled relative to front face 92, and the rear connection locations 80extend transversely relative to rear face 94.

[0064] Module 10 further includes opposed major planar sides 96, 98.Module 10 further includes opposed minor planar sides 100, 102 definingsides of module 10 in the embodiment shown. Major side 96 has sideextensions or flanges 104 which form slide rails for receipt in guides76 of chassis 70. The module and chassis interface may be configured inaccordance with commonly owned U.S. Pat. No. 5,363,465, which permitsthe modules to be flipped as they are moved from the left side to theright side and vice versa. Module 10 can be mounted vertically, ifdesired, instead of horizontally in a suitably configured chassis.

[0065] Module 10 includes a plurality of first adapters 106 a-e(generally 106) exposed along front face 92 for the front connectionlocations 80 for connection to fiber optic connectors 108. In the FIGS.only adapters 106 a and 106 e are shown, but adapters 106 b-d aresimilarly constructed. Adapters 106 are mounted to front face 92 byangled retainers 93, such as the type described and shown in U.S. Pat.No. 5,214,735. A plurality of second adapters 110 a,b (generally 110)are positioned along rear face 94 for the rear connection locations 80,also for connection to fiber optic connectors 112. The first and secondadapters 106, 110 are preferably positioned in linear arrays parallel tofront and rear faces 92, 94. The adapters shown are SC type, but couldalso be FC, ST, or any other suitable connection scheme. Two of thefirst adapters 106 (106 a,b) are used to cross-connect fiber opticequipment connected to the second adapters 110 a,b of module 10.Alternatively, module 10 can be interconnected to other equipment viafront adapters 106. In the illustrated embodiment, adapter 106 c definesa monitor port, and adapters 106 d,e are used as access locations suchas for connection to test equipment.

[0066] Module 10 includes two openings 111 which are not used in module10. Now with reference to FIGS. 5 and 6, an additional module 200 isshown. Module 200 is a double density module where two pieces ofequipment can be connected to module 200, for cross-connection throughmodule 200 at front adapters 106. Front adapters 106 are dual densityadapters.

[0067] Module 10 further includes end flanges 114 for use in mountingmodule 10 to chassis 70. Locking members 116 releasably hold flanges 114to chassis 70. Locking members 116 include spring loaded and retainedscrews. Other locking members, besides screws may be used as desired,such as the type shown and described in U.S. Pat. No. 5,363,465 whichoperate to lock or release by rotating 90°.

[0068] Modules 10, 200 are electrically powered and are connected to acontroller module 202 through a controller bus 204 of chassis 70. Plug95 connects each module 10 to bus 204.

[0069] Referring now to FIGS. 10-20, two modules 210, 212 are showncross-connected to one another in a system 208. Modules 210, 212 may bein the same chassis, or different chassis. Also modules 210, 212 may bein different locations altogether.

[0070] Modules 210, 212 are each also connected to test equipment 214.Test equipment 214 is shown as different test circuits which may not bepart of the same test unit. Optical 1×N switches 250, 252 connect thetest equipment 214 to modules 210, 212. Optical 1×N switches 254, 256also connect monitor test equipment 214 a, 214 b to modules 210, 212.The various switches 250, 252, 254, 256 can be remotely operated.Modules 210, 212 differ from module 10 in that instead of a 2×2 switch30 connecting the test equipment from the transmit signal pathway, a 2×2switch 216 connects the receive signal pathway to the test equipment.FIGS. 11-20 illustrate various applications of the two modules 210, 212.

[0071]FIG. 11 shows system 208 with modules 210, 212 operating in anormal or transparent mode in which the transmit signal of module 210from transmit port 230 is received at receive port 240. Further atransmit signal from transmit port 236 is received at receive port 234of module 210.

[0072]FIG. 12 illustrates system 208 in a transmit and receive loopbackmode once switches 24 are switched from the normal positions to theloopback positions. FIG. 13 illustrates use of system 200 in a loopbackmode for the test equipment by maintaining second switches 116 in thenormal position.

[0073]FIG. 14 illustrates system 208 in a split and loopback mode inwhich switch 24 is positioned in the loopback position, and switch 216of module 210 is positioned in the split position. FIG. 15 shows asimilar arrangement with respect to second module 212. FIG. 16 showsboth modules being operated in the split and loopback mode.

[0074]FIG. 17 shows system 208 being operated in a split mode where thetransmit signal of module 212 is received by the test equipment ofmodule 210. Further, the transmit signal from the test equipment isreceived by receive port 234 of module 210. FIG. 18 shows a transmitsignal from transmit port 230 being received by the test equipment ofmodule 212. The transmit signal of the test equipment of module 212 isreceived by receive port 240 of module 212. FIG. 19 shows both modules210, 212 being operated in the split mode.

[0075]FIG. 20 shows both modules 210, 212 being operated in the monitormode so as to monitor the output from both transmit ports 230, 236 ofthe respective test equipment.

[0076] Referring now to FIGS. 21-24, an alternative embodiment of amodule 310 is shown similar to module 10 including a first 2×2 switch24, but further including a 1×2 switch 320 instead of second switch 30.Module 310 also includes a splitter 332 and a monitor pathway 334 tomonitor test equipment. The 1×2 switch 320 allows for module 310 to bemanufactured more inexpensively since a 2×2 switch is avoided. However,no loopback to the test equipment is possible as for module 10. Also,only a portion (in the example shown, 10%) of the signal can be testedfrom terminal T1.

[0077] While the preferred embodiments show the modules 210, 212including the 2×2 switches 24, 30, it is to be appreciated that only onemodule in the circuit may be provided with the switching features.

[0078]FIG. 22 shows various features which may be utilized in thevarious possible configurations for module 310′ including positioning ofthe 1×2 switch in the receive signal pathway. Also, various monitors areshown for monitoring other portions of the signal pathways. FIG. 23shows schematically two modules cross-connected 310′, 310″, andincluding all of the various options available for the two modules.

[0079] Referring now to FIG. 24, two modules 310 are showncross-connected to one another in a system 308. Modules 310 may be inthe same chassis or different chassis. Also, modules 310 may be indifferent locations altogether.

[0080] Modules 310 are each also connected to test equipment 314. Testequipment 314 is shown as different test circuits which may not be partof the same test unit. As above in system 208, optical 1×N switches 350,352 connect the test equipment 314 to modules 310. The switches 350, 352can be remotely operated. System 308 can be operated under variousapplications depending on the positioning of switches 24, 320.

[0081] Referring now to FIGS. 25-27, two modules 310, 310 a are showncross-connected to one another in a system 308 a. Module 310 a is thesame as module 310, except module 310 a lacks a 2×2 switch 24. Costsavings may be realized for module 310 a due to its simpler design withless parts. FIGS. 26 and 27 show the loopback mode of operation (FIG.26) and the split and loopback mode of operation (FIG. 27) wherebyswitch 24 of module 310 is operated in order to achieve the loopbackrelative to module 310 a.

[0082] Referring now to FIGS. 28-39, a further preferred embodiment of amodule 410 is shown. Module 410 includes a single 2×2 switch 24positioned between first and second signal pathways 412, 414. Signalpathways 412, 414 link a first pair of fiber optic terminals 416 with asecond pair of terminals 418. Module 410 further includes a 1×2 switch420 in each signal pathway 412, 414. Further, module 410 also includes asplitter 432 and a monitor pathway 434 linked to monitor test equipmentin each signal pathway 412, 414. The 1×2 switches 420 allow for module410 to be manufactured more inexpensively since only three switches 24,420, 420 are provided. Module 410 is related to earlier describedmodules 10, 210, 212, 310, 310′, 310″, 310 a. However, module 410 wouldbe used instead of two of the above-noted modules which are described asbeing cross-connected together.

[0083]FIG. 29 shows module 410 connected to test equipment 414 andswitches 450, 452 in a system 408, in a similar manner as noted above insystems 208, 308. FIGS. 30-39 show various applications of system 408including module 410. FIG. 30 shows system 408 in the transparent modefor connection locations 460-463. FIG. 31 shows system 408 in a loopbackmode for connection locations 460-463. FIG. 32 shows system 408 wherethe test equipment 414 is utilized in a loopback mode. A loopbackcircuit is provided in connection with one of the pairs of ports of each1×N switch 450, 452. FIG. 33 shows a split and loopback mode for system408 with respect to connection locations 460 and 461. FIG. 34 showssystem 408 in a split and loop back mode with respect to connectionlocations 462 and 463. FIG. 35 shows system 408 where both pairs ofconnection locations 460 and 461, and 462 and 463 are in the split andloopback mode. FIG. 36 shows system 408 in a split mode for connectionlocations 460 and 461. FIG. 37 shows system 408 in a split mode withrespect to connection locations 462 and 463. FIG. 38 shows system 408where both pairs of connection locations are in a split mode. FIG. 39shows system 408 in a monitor mode.

[0084]FIG. 29 is illustrative of a system 408 in which separateindividual modules of the types described previously are not provided.Instead, the optical circuitry of system 408 may be provided in a singlemodule 410. It is to be appreciated that the various optical circuitsdescribed above for connecting telecommunications equipment, cables, andmonitor, test, and access equipment may be provided in a number ofphysical constructions, including the preferred modular constructionsnoted above. In addition, the circuitry can be provided on differentlyconfigured modules, an increased or decreased number of modules, or aspart of other frames, racks, or housings associated withtelecommunications and data connectivity systems. Similarly, thecross-connections noted above for individual modules, such as module 10,can be by patch cords including connectors matable with adapters ofmodule 10, or the connections can be by other optical links which may ormay not include patch cords. For example, an optical link may beprovided through controller bus 204 of chassis 70 shown in FIGS. 5 and6.

[0085] The above specification and examples provide a completedescription of the manufacture and use of the invention. Since manyembodiments of the invention can be made without departing from thespirit and scope of the invention, the invention resides in the claimshereinafter appended.

What is claimed is:
 1. A fiber optic circuit comprising: a) a pluralityof connection locations, wherein the plurality of connection locationsdefine first and second pairs of connection locations, each pairdefining first and second connection points; b) a first optical signalpathway between the first connection points; c) a second optical signalpathway between the second connection points; d) a first switch betweenthe first and second optical signal pathways wherein the switch hasfirst and second states. 1) the first state being a normal through statewherein the first connection points are optically linked along the firstoptical signal pathway, and wherein the second connection points areoptically linked along the second optical signal pathway; and 2) thesecond state being a loopback state wherein the first and secondconnection points of the first pair are in communication along a firstloopback path along a portion of the first and second optical signalpathways, and wherein the first and second connection points of thesecond pair are in communication along a second loopback path alongother portions of the first and second optical signal pathways.
 2. Thecircuit of claim 1, wherein the plurality of connection locations definea third pair of connection locations optically linkable with one of thefirst and second optical signal pathways.
 3. The circuit of claim 2,further comprising a second switch located in the first optical signalpathway between the first connection point of the first pair and thefirst switch, the second switch having two states: a) a first statebeing a normal state wherein the first connection point of the firstpair is optically linked with the first switch, and wherein the thirdpair of connection locations optically communicate with one anotheralong a loopback pathway; and b) a second state being a split statewherein the one of the connection locations of the third pair isoptically linked with the first connection point of the first pair, andwherein the other connection location of the third pair is opticallylinked with the first switch.
 4. The circuit of claim 3, furthercomprising a fourth pair of connection locations optically linkable withthe second optical signal pathway, and a third switch located in thesecond optical signal pathway between the second connection point of thesecond pair and the first switch, the second switch having two states:a) a first state being a normal state wherein the second connectionpoint of the second pair is optically linked with the first switch, andwherein the fourth pair of connection locations optically communicatewith one another along a loopback pathway; and b) a second state being asplit state wherein the one of the connection locations of the fourthpair is optically linked with the second connection point of the secondpair, and wherein the other connection location of the fourth pair isoptically linked with the first switch.
 5. The circuit of claim 3,further comprising a splitter in the second optical signal pathwaybetween the first switch and the second connection point of the firstpair, and a monitor connection location optically linked with thesplitter.
 6. The circuit of claim 3, further comprising a splitter inthe first optical signal pathway between the second switch and the firstconnection point of the first pair, and a monitor connection locationoptically linked with the splitter.
 7. The circuit of claim 1, furthercomprising: a) a module housing having front and rear faces, opposedmajor sides, and opposed minor sides defining an enclosed interior, thefront face including mounting flanges for mounting the module to achassis; b) a plurality of exposed adapters defining the connectionlocations along at least one of the front and rear faces, each of theplurality of adapters connectable to a fiber optic connector external tothe module.
 8. The circuit of claim 7, wherein the module housing andthe plurality of exposed adapters defines a first cross-connect module,further comprising a plurality of the first cross-connect modules, and aplurality of second cross-connect modules constructed and arranged asthe first cross-connect module, the first and second cross-connectmodules cross-connected together, and further comprising a plurality offirst and second test circuits, each test circuit including transmit andreceive signal connection locations, first and second dual 1×N opticalswitches, where N equals the number of the plurality of first and secondmodules cross-connected together, the first and second dual 1×N opticalswitches optically linked to the third signal connection locations ofthe plurality of first and second modules, and test equipment opticallylinked to the first and second dual 1×N optical switches.
 9. The circuitof claim 1, wherein the plurality of connection locations define a thirdconnection location optically linkable with one of the first and secondoptical signal pathways.
 10. The circuit of claim 9, further comprisinga second switch located in the first optical signal pathway between thefirst connection point of the first pair and the first switch, thesecond switch having two states: a) a first state being a normal statewherein the first connection point of the first pair is optically linkedwith the first switch, and wherein the third connection location isoptically isolated; and b) a second state being a split state whereinthe third connection location is optically linked with the first switch.11. The circuit of claim 9, further comprising a second switch locatedin the second optical signal pathway between the first connection pointof the first pair and the first switch, the second switch having twostates: a) a first state being a normal state wherein the firstconnection point of the first pair is optically linked with the firstswitch, and wherein the third connection location is optically isolated;and b) a second state being a split state wherein the third connectionlocation is optically linked with the first switch.
 12. The circuit ofclaim 10, further comprising a splitter in the first optical signalpathway between the second switch and the first connection point of thefirst pair, and a monitor connection location optically linked with thesplitter.
 13. The circuit of claim 11, further comprising a splitter inthe second optical signal pathway between the first and second switches,and a monitor connection location optically linked with the splitter.14. The circuit of claim 1, further comprising: a) a module housinghaving front and rear faces, opposed major sides, and opposed minorsides defining an enclosed interior, the front face including mountingflanges for mounting the module to a chassis; b) a plurality of exposedadapters defining the connection locations along at least one of thefront and rear faces, each of the plurality of adapters connectable to afiber optic connector external to the module.
 15. The circuit of claim14, wherein the module housing and the plurality of exposed adaptersdefines a first cross-connect module, further comprising a plurality ofthe first cross-connect modules, and a plurality of second cross-connectmodules constructed and arranged as the first cross-connect module, thefirst and second modules cross-connected together, and furthercomprising a plurality of first and second test circuits, each testcircuit including a main signal connection location and a monitor signalconnection location, first and second dual 1×N optical switches, where Nequals the number of plurality of first and second modulescross-connected together, the first and second dual 1×N optical switchesoptically linked to the main signal connection locations and the monitorsignal connection locations of the plurality of first and secondmodules, and test equipment optically linked to the first and seconddual 1×N optical switches.
 16. A fiber optic circuit comprising: a) aplurality of accessible optical circuits each including: 1) a pluralityof connection locations defining first and second transmit signalconnection locations and first and second receive signal connectionlocations; 2) a transmit signal pathway between the first and secondtransmit signal connection locations; 3) a receive signal pathwaybetween the first and second receive signal connection locations; 4) afirst switch between the transmit and receive signal pathways whereinthe switch has first and second states: A) the first state being anormal through state wherein the first and second transmit signalconnection locations are optically linked along the transmit signalpathway, and wherein the first and second receive signal connectionlocations are optically linked along the receive signal pathway; and B)the second state being a loopback state wherein the first transmitsignal connection location and the first receive signal connectionlocation are in communication along a first loopback path along aportion of the transmit and receive signal pathways, and wherein thesecond transmit signal connection location and the second receive signalconnection location are in communication along a second loopback pathalong other portions of the transmit and receive signal pathways; 5)wherein the plurality of connection locations define a third signalconnection location optically linkable through a second switch with oneof the transmit and receive signal pathways; 6) a remote controller forcontrolling operation of the first and second switches; b) optical linksbetween the second transmit and receive signal connection locations ofpairs of accessible circuits; c) a central controller and a networkconnecting the remote controllers.
 17. The system of claim 16, whereinthe second switch is located in the transmit signal pathway between thefirst transmit signal connection location and the first switch, thesecond switch having two states: a) a first state being a normal statewherein the first transmit signal connection location is opticallylinked with the first switch, and wherein the third signal connectionlocation is optically isolated; and b) a second state being a splitstate wherein the third receive signal connection location is opticallylinked with the first transmit signal connection location, and whereinthe third transmit signal connection location is optically linked withthe first switch.
 18. The system of claim 16, wherein the second switchis located in the receive signal pathway between the first receivesignal connection location and the first switch, the second switchhaving two states: a) a first state being a normal state wherein thefirst receive signal connection location is optically linked with thefirst switch, and wherein the third signal connection location isoptically isolated; and b) a second state being a split state whereinthe third transmit signal connection location is optically linked withthe first receive signal connection location, and wherein the thirdreceive signal connection location is optically linked with the firstswitch.
 19. The system of claim 17, further comprising a splitter in thetransmit signal pathway, and a monitor connection location opticallylinked with the splitter.
 20. The system of claim 18, further comprisinga splitter in the receive signal pathway, and a monitor connectionlocation optically linked with the splitter.
 21. A fiber optic circuitcomprising: a) first and second pairs of connection locations, each pairdefining first and second connection points; b) a first optical signalpathway between the first connection points; c) a second optical signalpathway between the second connection points; d) a first switch betweenthe first and second optical signal pathways wherein the first switchhas first and second states: 1) the first state being a normal throughstate wherein the first connection points are optically linked along thefirst optical signal pathway, and wherein the second connection pointsare optically linked along the second optical signal pathway; and 2) thesecond state being a loopback state wherein the first and secondconnection points of the first pair are in communication along a firstloopback path along a portion of the first and second optical signalpathways, and wherein the first and second connection points of thesecond pair are in communication along a second loopback path alongother portions of the first and second optical pathways; e) a secondswitch in the first optical signal pathway, and a third connection pointoptically linkable through the second switch with the first opticalsignal pathway, wherein the second switch is located between the firstconnection point of the first pair and the first switch, the secondswitch having two states: 1) a first state being a normal state whereinthe first connection point of the first pair is optically linked withthe first switch, and wherein the third connection point is opticallyisolated from the first optical signal pathway; and 2) a second statebeing a split state wherein the third connection point is opticallylinked with the first switch, and wherein the first connection point ofthe first pair is optically isolated from the first switch; f) a thirdswitch in the second optical signal pathway, and a fourth connectionpoint optically linkable through the third switch with the secondoptical signal pathway, wherein the third switch is located between thesecond connection point of the second pair and the first switch, thethird switch having two states: 1) a first state being a normal statewherein the second connection point of the second pair is opticallylinked with the first switch, and wherein the fourth connection point isoptically isolated from the second optical signal pathway; and 2) asecond state being a split state wherein the fourth connection point isoptically linked with the first switch, and wherein the secondconnection point of the second pair is optically isolated from the firstswitch.
 22. The circuit of claim 21, further comprising a splitter inthe first optical signal pathway, and a monitor connection pointoptically linked with the splitter.
 23. The circuit of claim 21, furthercomprising a splitter in the second optical signal pathway, and amonitor connection point optically linked with the splitter.
 24. Thecircuit of claim 21, wherein the third and fourth switches are 2×2switches.
 25. The circuit of claim 21, wherein the third and fourthswitches are 1×2 switches.
 26. A fiber optic cross-connect modulemountable to a chassis comprising: a) a module housing having front andrear faces, opposed major sides, and opposed minor sides defining anenclosed interior, the front face including mounting flanges formounting the module to the chassis; b) a plurality of exposed adaptersalong at least one of the front and rear faces, each of the plurality ofadapters connectable to a fiber optic connector external to the module;wherein the plurality of adapters define first and second transmitsignal ports and first and second receive signal ports; c) a transmitsignal pathway between the first and second transmit signal ports; d) areceive signal pathway between the first and second receive signalports; e) a first switch between the transmit and receive signalpathways wherein the switch has first and second states: 1) the firststate being a normal through state wherein the first and second transmitsignal ports are optically linked along the transmit signal pathway, andwherein the first and second receive signal ports are optically linkedalong the receive signal pathway; and 2) the second state being aloopback state wherein the first transmit signal port and the firstreceive signal port are in communication along a first loopback pathalong a portion of the transmit and receive signal pathways, and whereinthe second transmit signal port and the second receive signal port arein communication along a second loopback path along other portions ofthe transmit and receive signal pathways.
 27. The module of claim 26,wherein the plurality of exposed adapters define third transmit andreceive signal ports optically linkable with one of the transmit andreceive signal pathways.
 28. The module of claim 27, further comprisinga second switch located in the transmit signal pathway between the firsttransmit signal port and the first switch, the second switch having twostates: a) a first state being a normal state wherein the first transmitsignal port is optically linked with the first switch, and wherein thethird transmit and receive signal ports optically communicate with oneanother along a loopback pathway; and b) a second state being a splitstate wherein the third receive signal port is optically linked with thefirst transmit signal port, and wherein the third transmit signal portis optically linked with the first switch.
 29. The module of claim 27,further comprising a second switch located in the receive signal pathwaybetween the first receive signal port and the first switch, the secondswitch having two states: a) a first state being a normal state whereinthe first receive signal port is optically linked with the first switch,and wherein the third transmit and receive signal ports opticallycommunicate with one another along a loopback pathway; and b) a secondstate being a split state wherein the third transmit signal port isoptically linked with the first receive signal port, and wherein thethird receive signal port is optically linked with the first switch. 30.The module of claim 28, further comprising a splitter in the transmitsignal pathway, and a monitor port optically linked with the splitter.31. The module of claim 29, further comprising a splitter in the receivesignal pathway, and a monitor port optically linked with the splitter.32. The module of claim 28, wherein the module is a first module,further comprising a plurality of the first modules, and a plurality ofsecond modules constructed and arranged as the first module, the firstand second modules cross-connected together, and further comprising aplurality of first and second test circuits, each test circuit includingtransmit and receive signal ports, first and second dual 1×N opticalswitches, where N equals the number of the plurality of first and secondmodules cross-connected together, the first and second dual 1×N opticalswitches optically linked to the third transmit and receive signal portsof the plurality of first and second modules, and test equipmentoptically linked to the first and second dual 1×N optical switches. 33.The module of claim 29, wherein the module is a first module, furthercomprising a plurality of the first modules, and a plurality of secondmodules constructed and arranged as the first module, the first andsecond modules cross-connected together, and further comprising aplurality of first and second test circuits, each test circuit includingtransmit and receive signal ports, first and second dual 1×N opticalswitches, where N equals the number of the plurality of first and secondmodules cross-connected together, the first and second dual 1×N opticalswitches optically linked to the third transmit and receive signal portsof the plurality of first and second modules, and test equipmentoptically linked to the first and second dual 1×N optical switches. 34.The module of claim 26, wherein the plurality of exposed adapters definea third signal port optically linkable with one of the transmit andreceive signal pathways.
 35. The module of claim 34, further comprisinga second switch located in the transmit signal pathway between the firsttransmit signal port and the first switch, the second switch having twostates: a) a first state being a normal state wherein the first transmitsignal port is optically linked with the first switch, and wherein thethird signal port is optically isolated; and b) a second state being asplit state wherein the third signal port is optically linked with thefirst switch.
 36. The module of claim 34, further comprising a secondswitch located in the receive signal pathway between the first receivesignal port and the first switch, the second switch having two states:a) a first state being a normal state wherein the first receive signalport is optically linked with the first switch, and wherein the thirdsignal port is optically isolated; and b) a second state being a splitstate wherein the third signal port is optically linked with the firstswitch.
 37. The module of claim 35, further comprising a splitter in thetransmit signal pathway, and a monitor port optically linked with thesplitter.
 38. The module of claim 36, further comprising a splitter inthe receive signal pathway, and a monitor port optically linked with thesplitter.
 39. The module of claim 37, wherein the module is a firstmodule, further comprising a plurality of the first modules, and aplurality of second modules constructed and arranged as the firstmodule, the first and second modules cross-connected together, andfurther comprising a plurality of first and second test circuits, eachtest circuit including a main signal port and a monitor signal port,first and second dual 1×N optical switches, where N equals the number ofthe plurality of first and second modules cross-connected together, thefirst and second dual 1×N optical switches optically linked to the mainsignal ports and monitor signal ports of the plurality of first andsecond modules, and test equipment optically linked to the first andsecond dual 1×N optical switches.
 40. The module of claim 38, whereinthe module is a first module, further comprising a plurality of thefirst modules, and a plurality of second modules constructed andarranged as the first module, the first and second modulescross-connected together, and further comprising a plurality of firstand second test circuits, each test circuit including a main signal portand a monitor signal port, first and second dual 1×N optical switches,where N equals the number of plurality of first and second modulescross-connected together, the first and second dual 1×N optical switchesoptically linked to the main signal ports and the monitor signal portsof the plurality of first and second modules, and test equipmentoptically linked to the first and second dual 1×N optical switches. 41.A fiber optic cross-connect system comprising: a) a plurality of modulesincluding: 1) a plurality of connection locations connectable to a fiberoptic connector external to the module; wherein the plurality ofconnection locations define first and second transmit signal ports andfirst and second receive signal ports; 2) a transmit signal pathwaybetween the first and second transmit signal ports; 3) a receive signalpathway between the first and second receive signal ports; 4) a firstswitch between the transmit and receive signal pathways wherein theswitch has first and second states: A) the first state being a normalthrough state wherein the first and second transmit signal ports areoptically linked along the transmit signal pathway, and wherein thefirst and second receive signal ports are optically linked along thereceive signal pathway; and B) the second state being a loopback statewherein the first transmit signal port and the first receive signal portare in communication along a first loopback path along a portion of thetransmit and receive signal pathways, and wherein the second transmitsignal port and the second receive signal port are in communicationalong a second loopback path along other portions of the transmit andreceive signal pathways; 5) wherein the plurality of connectionlocations define third transmit and receive signal ports opticallylinkable through a second switch with one of the transmit and receivesignal pathways; 6) a remote controller for controlling operation of thefirst and second switches; b) optical cross connections between thesecond transmit and receive signal ports of pairs of modules; c) acentral controller and a network connecting the remote controllers. 42.The system of claim 41, wherein the second switch is located in thetransmit signal pathway between the first transmit signal port and thefirst switch, the second switch having two states: a) a first statebeing a normal state wherein the first transmit signal port is opticallylinked with the first switch, and wherein the third transmit and receivesignal ports optically communicate with one another; and b) a secondstate being a split state wherein the third receive signal port isoptically linked with the first transmit signal port, and wherein thethird transmit signal port is optically linked with the first switch.43. The system of claim 41, wherein the second switch is located in thereceive signal pathway between the first receive signal port and thefirst switch, the second switch having two states: a) a first statebeing a normal state wherein the first receive signal port is opticallylinked with the first switch, and wherein the third transmit and receivesignal ports optically communicate with one another; and b) a secondstate being a split state wherein the third transmit signal port isoptically linked with the first receive signal port, and wherein thethird receive signal port is optically linked with the first switch. 44.The system of claim 42, further comprising a splitter in the transmitsignal pathway, and a monitor port optically linked with the splitter.45. The system of claim 43, further comprising a splitter in the receivesignal pathway, and a monitor port optically linked with the splitter.46. A fiber optic circuit comprising: a first optical signal pathwaybetween first and second connection points; a second optical signalpathway between third and fourth connection points; means forselectively isolating the first and second connection points and thethird and fourth connection points, and further linking the first andsecond optical signal pathways so as to provide a loop back between thefirst and third connection points, and between the second and fourthconnection points; means for providing access to the first opticalsignal pathway to optically link fifth and sixth connection points tothe first optical signal pathway.
 47. The fiber optic circuit of claim46, further comprising means for providing access to the second opticalsignal pathway to optically link seventh and eighth connection points tothe second optical signal pathway.